Ana C. Brito

Changes in the Phytoplankton Composition in a Temperate Estuarine System (1960 to 2010)

The main aim of this study was to evaluate the temporal changes in the phytoplankton community of the Tagus Estuary and to identify the stressors involved. Environmental and phytoplankton data were gathered from several studies conducted in the 1960s, 1980s and from 1999 to 2010 (2000s). Phytoplankton data included information on the community composition through microscopy. No significant change was found between temperature and nitrogen values in the three periods. Chlorophyll a concentrations varied throughout the years, and the lowest concentrations were observed after 2004. Significant differences were also found between phytoplankton cell abundances, lower in the 1980s compared to the ones recorded in the 2000s. In the 1980s, diatoms were the most abundant group in the majority of samples and were found to be associated with nitrogen concentrations (canonical correspondence analysis), which was not observed in the 2000s. In the period 2006–2007, the importance of diatoms decreased and smaller cells became more abundant (e.g. cryptophytes, euglenophytes, prasinophytes). The ratio cryptophyta/bacillariophyta seems to yield an increase from <1 in 1980s to >1 in 2006–2007. Mesodinium rubrum and Dinophysis produce recurrent toxic blooms in the adjacent coastal area. We can speculate that the estuary can be a cryptophyte producer to sustain the cryptophytes-M. rubrum-Dinophysis trophic relationship. A top-down hypothesis (shellfish grazing) is considered to explain the change in the phytoplankton community. A quantitative tool, the Phytoplankton Community Index (PCI), yielded a significant deviation of the community, from the 1980s to the 2000s, suggesting a shift toward the dominance of small cells.

Measuring Light Attenuation in Shallow Coastal Systems

Photosynthetic Active Radiation (PAR) was measured using single planar and two-bulb spherical light sensors. The attenuation coefficient (Kd) was found to vary significantly during the year. The highest Kd values were obtained in the station with higher influence of currents and run-off. Our data suggested a reflection of 50% of light that reaches the bottom, which is associated with a decrease in the Kd value obtained with the spherical sensor of 0.15 m-1. This means that flat sensors may underestimate PAR and that spherical sensor may underestimate Kd. This is a critical issue given that knowledge on light attenuation is essential for modeling approaches and quality assessments.

The Role of Science in Society: Challenges in a Time of Global Changes

What is the role of science in society? Is science improving our ability of living in a sustainable way? Does science communicate effectively with society? In a societal point of view, science should provide solutions to our daily problems, as well as to technical and philosophical issues [1]. Science should enhance the quality level of responses provided to society. On the other hand, science requires a high level of support from society. The financial support is perhaps the most visible, and of course, a critical issue in managing science. However, science also needs to engage in communication with society. Feedback and understanding from the common citizen is essential to improve science and to protect the natural environment [2]. Nevertheless, communication between scientists, managers and policy makers still represents a major challenge.